1. Field of the Invention
The present invention relates to packet-data cellular telecommunications, particularly to a method and system for Mobile IP Registration (MIP) of a Mobile Node during a dormant hand-off in a CDMA 2000 packet-data cellular telecommunications network.
2. Description of the Related Art
The CDMA 2000 cellular telecommunications network is a third generation (3G) cellular telecommunications network that uses the Code Division Multiple Access (CDMA) radio access technology for providing high-speed wireless service to mobile stations (MS). The services include two-way transmission of voice, text, multimedia applications, and movies, as well as internet access.
An exemplary IP-based CDMA 2000 cellular telecommunications network includes a plurality of mobile stations herein designated as Mobile Nodes (MNs) communicating over a radio interface with Base Transceiver Stations (BTS). Each group of one or more BTSs is connected to, and controlled by a Base Station Controller (BSC), while each group of BSCs of one particular packet zone are controlled by one Packet Control Function (PCF), which purpose is to manage the access network connectivity to the PDSN for 3G packet data services. Thus, typically, a given BSC can only be serviced by a given PCF. One or more Mobile Switching Centers (MSCs) may be connected to the CDMA 2000 cellular packet data telecommunications network for the provision of cellular service to subscribers and for mobility management (authentication and traffic channel assignments), while a Packet Data Service Node (PDSN) performs the switching and routing functions directed to the packet data communications within the CDMA 2000 cellular telecommunications network, and the logical support and assignment of IP-based (packet data) services.
The CDMA 2000 packet-data cellular telecommunications network provides Mobile IP service to packet mobile users as described in the standard “Wireless IP Standard IS-835”, herein included by reference. Mobile IP service is provided over a Point-to-Point Protocol (PPP) connection between the MN and the PDSN. When a PPP connection is established, negotiation messages are exchanged between the MN and the PDSN with regards to authentication and compression, followed by the MN's Mobile IP (MIP) registration. Thereafter, data may be sent from and to the MN, such as for example during a file download. However, the MN becomes dormant when no data is transmitted for a certain period of time over the PPP connection. In instances when the MN is dormant, there is no traffic channel assigned for the MN, although the PPP connection is maintained in both the MN and the PDSN.
When a dormant MN moves within the packet data service area, instances arise when the MN is handed-off, from a first packet zone to a second packet zone. However, in the source packet zone, the original PPP connection is maintained in both the PDSN and the MN for a predefined period of time even after the MN is handed-off to the target packet zone. When the dormant MN moves from one packet zone to another, the MN notifies the access network, and a Packet Control Function (PCF) within the access network attempts to select a PDSN for the MN. The goal is to try to select the same PDSN where a PPP session is maintained for the mobile IP user. However, oftentimes, depending upon the network configuration, the result of the selection will not be the same PDSN, and the MN could end up being handed-off to a PDSN which already holds an unexpired PPP connection and an unexpired MIP registration for that MN. In such a case, the standard version IOS V. 4.0 stipulates that A11 registration procedures shall not be performed since both the PDSN and PCF already have an active A10 physical connection between the BSC/PCF and the PDSN (the A10 physical connection being also called herein a Radio network Packet data serving node session or connection, (RP connection)). However, in the current implementations compliant with the existing standard, in such a scenario the Home Agent (HA) fails to be updated with the new care-of-address containing the serving PDSN identification, which results in data from the MN being sent to the wrong PDSN, i.e. to the source PDSN.
The same problem arises in cases wherein the situation is further complicated by the likelihood that while performing a dormant hand-off between different PDSNs, the MN could suddenly request reactivation of the packet data call before issuing an origination request indicating that it is performing dormant mobility. Should this scenario occur, there is no way for the system to recognize that the transaction is effectively, at first, a dormant mobility event. Thus, no agent advertisement is sent, which results in temporary loss of data in the downstream direction.
It would be advantageous to have a method that solves the above-identified deficiency. In particular, there is an advantage to have a simple and straightforward method that on one hand, takes advantage of the existing features of the CDMA2000, and on the other hand modifies the existing standard, for allowing the proper PDSN to be registered with the Home Agent in cases of dormant mobility events.